[flake8-bugbear] don't fix B009/B010 if identifier would be mangled

fixes #2202

resources/test/fixtures/flake8_bugbear/B009_B010.py

@@ -1,7 +1,7 @@
 """
 Should emit:
-B009 - Line 18, 19, 20, 21, 22
-B010 - Line 33, 34, 35, 36
+B009 - Line 18, 19, 20, 21, 22, 23, 24
+B010 - Line 39, 40, 41, 42, 43, 44, 45
 """
 
 # Valid getattr usage
@@ -17,6 +17,8 @@
 # Invalid usage
 getattr(foo, "bar")
 getattr(foo, "_123abc")
+getattr(foo, "__123abc")
+getattr(foo, "__123abc__")
 getattr(foo, "abc123")
 getattr(foo, r"abc123")
 _ = lambda x: getattr(x, "bar")
@@ -36,6 +38,8 @@
 # Invalid usage
 setattr(foo, "bar", None)
 setattr(foo, "_123abc", None)
+setattr(foo, "__123abc", None)
+setattr(foo, "__123abc__", None)
 setattr(foo, "abc123", None)
 setattr(foo, r"abc123", None)
 setattr(foo.bar, r"baz", None)

src/rules/flake8_bugbear/rules/getattr_with_constant.rs

@@ -21,6 +21,10 @@ fn attribute(value: &Expr, attr: &str) -> Expr {
     )
 }
 
+fn is_mangled_private(id: &str) -> bool {
+    id.starts_with("__") && !id.ends_with("__")
+}
+
 /// B009
 pub fn getattr_with_constant(checker: &mut Checker, expr: &Expr, func: &Expr, args: &[Expr]) {
     let ExprKind::Name { id, .. } = &func.node else {
@@ -47,7 +51,9 @@ pub fn getattr_with_constant(checker: &mut Checker, expr: &Expr, func: &Expr, ar
 
     let mut diagnostic =
         Diagnostic::new(violations::GetAttrWithConstant, Range::from_located(expr));
-    if checker.patch(diagnostic.kind.rule()) {
+
+    // Don't autofix if name would be mangled by Python's "private variables" handling
+    if checker.patch(diagnostic.kind.rule()) && !is_mangled_private(value.as_str()) {
         diagnostic.amend(Fix::replacement(
             unparse_expr(&attribute(obj, value), checker.stylist),
             expr.location,

src/rules/flake8_bugbear/snapshots/ruff__rules__flake8_bugbear__tests__B009_B009_B010.py.snap

@@ -45,69 +45,97 @@ expression: diagnostics
     column: 0
   end_location:
     row: 20
+    column: 24
+  fix: ~
+  parent: ~
+- kind:
+    GetAttrWithConstant: ~
+  location:
+    row: 21
+    column: 0
+  end_location:
+    row: 21
+    column: 26
+  fix:
+    content:
+      - foo.__123abc__
+    location:
+      row: 21
+      column: 0
+    end_location:
+      row: 21
+      column: 26
+  parent: ~
+- kind:
+    GetAttrWithConstant: ~
+  location:
+    row: 22
+    column: 0
+  end_location:
+    row: 22
     column: 22
   fix:
     content:
       - foo.abc123
     location:
-      row: 20
+      row: 22
       column: 0
     end_location:
-      row: 20
+      row: 22
       column: 22
   parent: ~
 - kind:
     GetAttrWithConstant: ~
   location:
-    row: 21
+    row: 23
     column: 0
   end_location:
-    row: 21
+    row: 23
     column: 23
   fix:
     content:
       - foo.abc123
     location:
-      row: 21
+      row: 23
       column: 0
     end_location:
-      row: 21
+      row: 23
       column: 23
   parent: ~
 - kind:
     GetAttrWithConstant: ~
   location:
-    row: 22
+    row: 24
     column: 14
   end_location:
-    row: 22
+    row: 24
     column: 31
   fix:
     content:
       - x.bar
     location:
-      row: 22
+      row: 24
       column: 14
     end_location:
-      row: 22
+      row: 24
       column: 31
   parent: ~
 - kind:
     GetAttrWithConstant: ~
   location:
-    row: 23
+    row: 25
     column: 3
   end_location:
-    row: 23
+    row: 25
     column: 20
   fix:
     content:
       - x.bar
     location:
-      row: 23
+      row: 25
       column: 3
     end_location:
-      row: 23
+      row: 25
       column: 20
   parent: ~
 

src/rules/flake8_bugbear/snapshots/ruff__rules__flake8_bugbear__tests__B010_B009_B010.py.snap

@@ -5,91 +5,127 @@ expression: diagnostics
 - kind:
     SetAttrWithConstant: ~
   location:
-    row: 37
+    row: 39
     column: 0
   end_location:
-    row: 37
+    row: 39
     column: 25
   fix:
     content:
       - foo.bar = None
     location:
-      row: 37
+      row: 39
       column: 0
     end_location:
-      row: 37
+      row: 39
       column: 25
   parent: ~
 - kind:
     SetAttrWithConstant: ~
   location:
-    row: 38
+    row: 40
     column: 0
   end_location:
-    row: 38
+    row: 40
     column: 29
   fix:
     content:
       - foo._123abc = None
     location:
-      row: 38
+      row: 40
       column: 0
     end_location:
-      row: 38
+      row: 40
       column: 29
   parent: ~
 - kind:
     SetAttrWithConstant: ~
   location:
-    row: 39
+    row: 41
     column: 0
   end_location:
-    row: 39
+    row: 41
+    column: 30
+  fix:
+    content:
+      - foo.__123abc = None
+    location:
+      row: 41
+      column: 0
+    end_location:
+      row: 41
+      column: 30
+  parent: ~
+- kind:
+    SetAttrWithConstant: ~
+  location:
+    row: 42
+    column: 0
+  end_location:
+    row: 42
+    column: 32
+  fix:
+    content:
+      - foo.__123abc__ = None
+    location:
+      row: 42
+      column: 0
+    end_location:
+      row: 42
+      column: 32
+  parent: ~
+- kind:
+    SetAttrWithConstant: ~
+  location:
+    row: 43
+    column: 0
+  end_location:
+    row: 43
     column: 28
   fix:
     content:
       - foo.abc123 = None
     location:
-      row: 39
+      row: 43
       column: 0
     end_location:
-      row: 39
+      row: 43
       column: 28
   parent: ~
 - kind:
     SetAttrWithConstant: ~
   location:
-    row: 40
+    row: 44
     column: 0
   end_location:
-    row: 40
+    row: 44
     column: 29
   fix:
     content:
       - foo.abc123 = None
     location:
-      row: 40
+      row: 44
       column: 0
     end_location:
-      row: 40
+      row: 44
       column: 29
   parent: ~
 - kind:
     SetAttrWithConstant: ~
   location:
-    row: 41
+    row: 45
     column: 0
   end_location:
-    row: 41
+    row: 45
     column: 30
   fix:
     content:
       - foo.bar.baz = None
     location:
-      row: 41
+      row: 45
       column: 0
     end_location:
-      row: 41
+      row: 45
       column: 30
   parent: ~